Composite structural product and method of making the same



Patented Oct. 26, 1937 UNITED STATES PATENT OFFICE COMPOSITE STRUCTURALPRODUCT AND METHOD OF MAKING THE SAME Paul Schwarzkopf, Reutte, Tyrol,Austria 9 Claims.

This invention relates to a composite structural material and shapedarticles made therefrom intended more particularly for electricalpurposes without however being limited to such use.

In particular this application forms a continuation in part of myco-pending application, Ser. No. 594,154, filed February 19, 1932 issuedas Patent No. 2,030,229, on February 11, 1936.

Numerous composite structural materials, more particularly alloys of thevarious heavy and light metals, have already been proposed. They havebeen designed to yield particular strength with a low density or readyshaping capability; they frequently also unite high electricalconductivity with low density and suificient mechanical strength. Moreparticularly importance has been attached to a content of higher meltingand hard constituents, such as tungsten, molybdenum, tantalum, whilstthe greater shaping capability, more particularly the adaptability forbeing poured or cast and for being mechanically worked, has been yieldedby softer or lower melting metals, such as copper or silver.

This invention relates to a structural material (conglomerate) andshaped articles made therefrom which consists of material taken fromeach of the following two groups: molybdenum, titanium, vanadium,tungsten, tantalum, as a first group and silver, gold, aluminium,cobalt, chromium, copper, nickel, platinum, tin, zinc, iron, as a secondgroup, such material being obtained in the hot and/or under pressure asa conglomerate, which exhibits, therefore, no chemical combinationbetween the several elements but on the contrary a solid mixture, solidsolution or permeation of at least two constituents.

According to the invention, the material of the first group 'is used ina special granular texture.

The preparation of tungsten and molybdenum suitable for the purposes ofthe invention may be described first.

A known process for obtaining tungsten and molybdenum consists inobtaining from the ore an oxide of the metal in the gaseous or vapourstate by sublimation and precipitating the same by condensatiorf. Themetal is obtained from, the resulting oxide by reduction. This reductionmay be carried out in such a way, e. g. retarded, that as a. result ofthe reduction and the heat evolution accompanying the same, a metalpowder is obtained which is more coarsely granulated than that obtainedby the normal method of production. Since the reaction velocity duringthe reduction depends both on the temperature as well as on theconcentration of the reducing agent in the reducing gas mixture, then byadjusting one of these factors, or both factors, the course of thereduction may be retarded as desired and as a result the formation 5 oflarger crystals, that is to say the production of a coarsely granulatedpowder, promoted. If operations are carried out with reducing hydrogen,then steam may, for example, be mixed with the same for this purpose.

Another way of obtaining the special texture of the material of thefirst group is explained more in detail in my co-pending applicationSer. No. 594,154, and consists in sintering or smelting into a coherentbody the crystals of which are coarser than the granulation of thestarting powder, then hammering the sintered or fused body andcommlnuting it until a powder of the desired coarse granule is obtained.

In order to make a conglomerate usable for this invention, the powder isthen mixed with the softer or lower melting metal powders and heated, abody may be obtained which, according to the mixing proportions, showsdesired physical, electrical and mechanical properties.

The metal of the second group may be present in quantities of 3-6% if itis to act merely as a binder, and in larger quantities, up to about 15%of the body obtained, if it is also decisively 30 to influence otherproperties of the body, such as its surface quality. For many purposesit will be advantageous to use the lower melting or soft metals inquantities up to -90%.

The following binary compositions are particularly advantageous for usewith this invention:

Tungsten-silver; tungsten-chromium; tungsten-copper; tungsten-tin;tungsten-zinc; molybdenum-silver; molybdenum-copper; molybdenumchromium;molybdenum-tin; molybdenumzmc.

The following ternary compositions are particularly advantageous:

Molybdenum-nickel-copper; molybdenum-silver-chromium;molybdenum-chromium-copper; tungsten-nickel-copper;tungsten-silver-copper; tungsten-copper-chromium; tungsten coppertin.

In order to make this conglomerate material the procedure adopted issuch that the coarsely granular highermelting metal powder obtained iscast over with the liquid soft metals, or the powders are mixed andheated until at last the soft metal melts, or both these procedures arecombined. Whole blocks of any desired shape and size can be obtained inthis way which are either homogeneous or which contain the hard metal inlarger quantities in some parts and the soft metal in larger quantitiesin other parts. Such layering may, for example, be produced by mixingthe soft and hard metals, causing the soft metals to melt, and thenallowing the hot bath to subside, as a result of which a more or lessconsiderable demixing occurs and the heavier metals collect in largerquantities, i. e. concentrate, at desired places.

The material obtained in this way may be mechanically worked; moreparticularly it may be extended by hammering or rolling and the sheetsobtained punched and pressed.

It is a well-known fact that the union of higher melting metals liketungsten and molybdenum with other bodies oifers difllculties. Suchbodies of high melting point are frequently chosen since they can beheated to a higher temperature during use, and the union with a supportmust then be effected with the aid of a hard solder. As a rule whensoldering undesirable oxidation apcal pressure.

pears on the tungsten etc. body. For many purposes also tungsten etc.bodies are required having a compact surface (high lustre) which offersresistance to corrosion. Such compact bodies, however, can be producedonly by mechanical working, for example, by rolling out tungsten sheetsof extraordinary thinness. If now bodies are shaped or cut from suchsheets and united with other bodies by means of hard solders, thenmerely the compact skin is lost by oxidation.

According to the invention sheets of tungsten, molybdenum and so forthare made of the desired thickness, and also sheets of a conglomerate ofthe kindabove described, e. g. of coppertungsten, and these two sheetsare layed one upon the other and united in the hot,advantageouslyinareducing atmosphere and by mechani- The sheets blendtogether and a unitary sheet is obtained which consists of tungstenon-one side and of copper-tungsten on the other side. However,copper-tungsten is easy to solder. In addition the tungsten on thecoppertungsten side can be dissolved out, erg. by etching with potassiumnitrite, so that a sheet is obtained which consists of tungsten on oneside and to a greater or less extent of pure copper on the other side.The union between these two parts is extraordinarily intimate and theycannot be separated either during subsequent working or duringoperation. No perceptible electrical transition resistance can bedetected and nor is it to be expected since non-conducting oxides areabsent.

The procedure may also be such that a sheet of copper-tungsten is laidon' a tungsten sheet of any desired thickness or thinness and on top ofthe same a sheet of copper is placed, and the three sheets are united toa three-fold sheet in the hot and in a reducing atmosphere andpreferably with employment of a suitable pressure. Once again thecopper-tungsten is intimately and inseparably united both with thetungsten and with the copper. In this case the chemical treatment of thecopper-tungsten for the purpose of dissolving out the tungsten isdispensed with. This latter process is frequently of advantage sincepores are formed in the copper owing to the dissolution of the tungstenwhich are desirable for soldering purposes.

A further method consists in rolling out a block of copper-tungstenprepared as being described above and which consists for the most partof tungsten on the one side and on the other side for the most part orexclusively of copper in the direction of the layers whereby a sheet isobtained which on one side consists for the most part or exclusively oftungsten and on the other side for the most part or exclusively ofcopper. A tungsten sheet can be united with this sheet on the sideconsisting for the most part of tungsten in the manner previouslydescribed, should the sheet not be forthwith suitable for the purpose inview.

Sheets obtained in this way may be of .any desired thickness orthinness; the thickness of three-fold sheets can always be considerablyless than 1 mm. since the individual sheets can be rolled outtothicknesses amounting to a fraction of a millimetre (e. g. mm.).

If electric contacts are stamped out of such a sheet then these can beunited with the support, e. g. iron or aluminium spring, by softsoldering, all oxidation and structural change in the Joined part beingexcluded. Sheets obtained in the said way may also be coated with tin onthe copper side, or a sheet of tungsten-copper-tin may be made first ofall when the soldering is particularly facilitated and solderingtemperatures of 230 C. and less may be employed. 'No oxidation norimpairing of the mirror-smooth highly lustrous rolled surface of thetungsten can take place, which latter surface on account of its greatcompactness is substantially more resistant to corrosion .and oxidationthan the surfaces of known contacts. If, however, as has been frequenthitherto, the contacts must be hardsoldered with nickel or nickel alloysor even welded then oxidation of the tungsten-body is unavoidable, thecompact rolled surface disappears and of course the contact surfacecannot be produced again even by subsequent rubbing with emery orpolishing. It is obvious that by such heat treatment steel springs orspecial alloys which rust only with difliculty are impaired. In additionthe expedient of welding the tungsten contact on to an iron base firstof all which in turn is united with the support has, quite apart fromits cost, afforded no permanent help.

A further advantage of the invention, how-- ever, consists in'this thatcontacts can now be made from the thinnest sheet tungsten, which is madeof a thinness approaching that of a skin (about mm. thick) and united tothe support by means of soft soldering with the aid of the connectinglayer. This expedient can be adopted in all cases in which particularheating does not arise during the operation, as, for example, in thecase of telephone contacts (more particularly for contact springs inautomatic telephony), which must not oxidize and must occupy as littlespace as possible.

-Double or multi-layered sheet made in the manner described can also bepressed in an astonishing manner in the cold or under conditions ofslight heat. Obviously the thin tungsten sheet is made more shapeable(i. e. plastic) owing to its ideal union with the still more ductilecoppertungsten sheet. A body made in this way can then be used as suchor after removal of the copper by,chemica1 means (dissolution in nitricacid). The tungsten skeleton remaining after dissolution of the coppercan then be rubbed down, scraped ofi or ground 01!. In this way it ispossible to make even complicated articles of tungsten, molybdenum andso forth, such as, for example, calottes or bodies of revolution, suchas hitherto for many purposes (Rontgen electrodes) could be made only atmuch cost and trouble by difiicult casting operations.

It may be said in general that the invention enables either diificultlymelting or hard bodies to be coated, more particularly plated, with lowmelting or softer bodies to any desired thickness on one or both sides,or vice versa low melting or soft bodies to be coated or plated withhigher melting or harder bodies on one or both sides. The union is inevery case efiected in the heat with suitable mechanical pressure andabsence of oxidizing agents.

The invention is not in any way limited to the procedures set forth inthe examples given. It may be used, for example, for loom motor switcheswhich as is well known are subjected to a very great mechanical wear.The contact of such a switch has approximately a double T-cross sectionand according to the invention is made for the most part from a copperrod which is provided on one side with a layer of copper-tungsten and isthen drawn or rolled into the desired section, so that a copper rail isobtained which has one surface of copper-tungsten and from which acontact of the desired length can be cut oil. In a similar way, fromround copper rods which are coated completely with a copper-tungstenlayer it is possible to draw tubes or wires which consist on theexterior of coppertungsten and in the interior of copper.

Although here conglomerate bodies of any desired shapes, such as wiresand sheet, consisting of tungsten and copper have been more particularlydescribed, yet the process may be employed to every other conglomeratebody such as has been set forth in the introduction. Thus, for manypurposes aluminium bodies with tungsten or molybdenum layers, as well ascopper bodies with tungsten layers, are to be recommended.

What I claim is:

1. A composite article consisting of metal taken from a first group,comprising tungsten, molybdenum, tantalum, and at least one metal takenfrom a second group, comprising silver, gold, aluminum, cobalt,chromium, iron, copper, nickel, platinum, tin, zinc, titanium, saidarticle consisting of at least two parts intimately connected witheachother, one part consisting substantially of coherent metal of thefirst group, another part consisting of metal of the first and secondgroups, the metals of both groups present in the body being chosen sothat they do not substantially combine or form solid solutions, themetal of the first group consisting of particles being coarser than theoriginal metal powder and forming at least .part of a working or freesurface of said article.

2. A composite article as claimed in claim 1, in which at least onemetal of the second group forms a solidified melt, and the metal of thesecond group amounts to between about 3 to 90% of the article.

' 3. A composite article as claimed in claim 1, the part consistingsubstantially of metals of the first group being thinner than about 1mm. and forming a sheet, and the second part forming a layer thereon.

4. A composite article as claimed in claim 1, in which both parts formsheets intimately con= nected with each other.

5. A composite article according to claim 1, comprising a. coherentlayer consisting substantially of material of the first group, anotherlayer intimately connected with the first one and consisting of metaltaken from the first and the second group, and a third layer intimatelyconnected with the second one and consisting substantially of metaltaken from the second group.

6. A method of manufacturing a composite article, shaped into a sheet,comprising heating metal powder taken from a first group comprisingtungsten, molybdenum, tantalum, to at least sintering temperature,comminuting the coherent solid body so obtained to particles beingcoarser than the original metal powder, uniting said particles by atleast one metal taken from a second group comprising silver, gold,aluminum, cobalt, chromium, iron, copper, nickel, platinum, tin, zinc,titanium, rolling the body so. obtained into a sheet, combining saidsheet with another one, consisting substantially of metal taken from thefirst group and adapted to form at least part of a working or freesurface.

7. A- method as claimed in claim 6, supplemented by the steps of addinga further layer, substantially consisting of metal of the second group,and uniting such layer with that consisting of metal of the first andsecond group in the heat, but below sintering temperature of the metalof the first group.

8. A composite article comprising one part adapted to form a working orfree surface, said part consisting substantially of coherent metal takenfrom a first group comprising tungsten, molybdenum and tantalum, asecond part intimately connected with the first one, and consisting ofmetal of the first and of a second group, comprising silver, gold.aluminum, cobalt, chromium, iron, copper, nickel, platinum, tin, zinc,titanium, and a third part intimately connected with the second one, andconsisting substantially of metal of said second group.

9. A composite article according to claim 8,

being formed into a sheet, comprising a sheet consisting substantiallyof metal taken from the first group, another sheet, intimately connectedwith the first one and consisting of metal taken

